Water gates are employed in a range of impound docks, marinas and canals in order to protect vessels from the detrimental effects of tides, wind and waves. Similarly such gates are employed within lock mechanisms so as to permit vessels to move up and down from one water level to another within a canal.
A further area where water gates are employed is in the construction of flood control barriers. Typically, a number of gates are located across a river estuary and are deployed at times when tide levels rise to such a point that there is a significant danger of flooding of the surrounding area.
In order for existing flood control barriers designs to provide the necessary protection their construction requires substantial civil engineering work that includes the installation of concrete caissons. A good example of such a flood control barrier is the Thames Barrier. Such structures are therefore extremely expensive and their installation can seriously disturb the habitat of the sub-sea life forms and the surrounding environment.
The Prior Art teaches of Mitre, Sector, Radial and Flap style water gates employed for the aforementioned purposes. These all comprise steel core structures with various means for providing the required watertight seal. However, for various reasons these gate designs are prone to leakage.
In the UK alone 73% of ports that employ Mitre gates exhibit substantial levels of leakage. Such leaks cost time and the associated water losses can render the port unattractive and ultimately inoperable. Replacement gates cost in the region of .English Pound.800,000 and have a lifetime of about 30 to 50 years. However, Mitre gates require major maintenance work every 10 to 15 years that typically incurs costs of .English Pound.200,000.
In addition the effects of global warming are reducing the efficiency of Mitre gates due to increases in the associated water levels. These gates depend upon hydraulic pressure that results from the difference in the water levels from the upper side and lower side of the Mitre gate. Such increased water levels act to reduce this difference hence reducing the gate efficiency.
A second disadvantage of such gate designs is the fact that they employ hardwoods in order to provide the required watertight seals. These woods are expensive due to their limited supply and so a more environmentally friendly solution would be preferable.
Presently, Sector gates are the preferred option for replacing Mitre Gates. Although the gates themselves offer an economical alternative to the Mitre Gate they require extensive civil engineering work to be carried out to provide the required Sector gate recesses. Such civil engineering is both time consuming and expensive incurring costs of several millions of pounds.